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Biology🧬 > Nervous System💪🏻 > Flashcards

Nervous System💪🏻 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the steps in a response?

A
  • Stimulus
  • Receptor
  • CNS
  • Effector (muscle or gland)
  • Response
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2
Q

What are neurones?

A
  • Basic functional unit of the nervous system

* Highly specialised cells that are able to generate and transmit nerve impulses

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3
Q

What is the cell body? (Neurones)

A

Contains nucleus, nucleolus and other organelles (including ribosomes - neurotransmitters and mitochondria - Na+/K+ pump

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4
Q

What is a dendrite? (Neurones)

A
  • Thin cytoplasmic extensions which carry impulses towards the cell body
  • Relatively short in motor neurone and able to communicate with other neurones
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5
Q

What is an axon? (Neurones)

A
  • Carries impulses away from the cell body
  • Form connections with a muscle of gland at motor end plates
  • Numerous mitochondria in branched ends - involved in synthesis of transmitter substances
  • Myelinated axon has a fatty sheath of myelin
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6
Q

What are Schwann cells? (Neurones)

A
  • Wrap themselves around the axon, along its length

* Results in several layers of fatty myelin surrounding axon

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7
Q

What are the nodes of Ranvier? (Neurones)

A
  • Gaps between adjacent Schwann cells

* Here, axon is exposed - no myelin

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8
Q

What is the effect of the myelin sheath?

A

Increases the rate of transmission of impulses along the axon

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9
Q

What is the difference between sensory and motor neurones?

A
  • Sensory - one long dendrite bringing information

* Motor - one long axon taking information away

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10
Q

What is the spinal cord?

A

A hollow tube running from the base of the brain to the end of the spine

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11
Q

What is grey matter? (Spinal cord)

A
  • Central

* Contains cell bodies of relay and motor neurones

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12
Q

What is white matter? (Spinal cord)

A
  • Outer

* Contains myelinated axons which run up and down the spinal cord, to and from the brain

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13
Q

What is the spinal canal? (Spinal cord)

A
  • Centre of the grey matter

* Nutritive cerebrospinal fluid circulates through this

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14
Q

What is the dorsal root ganglion? (Spinal cord)

A
  • Sensory neurones enter spinal cord via dorsal root

* Concentration of their cell bodies forms a swelling

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15
Q

What is the ventral root? (Spinal cord)

A

Motor neurones leave via ventral root

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16
Q

What is a reflex?

A
  • An automatic, rapid response to an adverse stimulus

* The neurones that are involved in making a reflex occur make up a reflex arc

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17
Q

How is the resting potential generated?

A 
•In a resting axon:
-high conc. of Na+ outside
-high conc. of K+ inside
•Membrane is polarised 
•Net effect - inside is negative compared to outside giving the resting potential
•K+ leakage channels - K+ leaks out
•Na+/K+ pump - 3Na+ out, 2K+ in
•Negative particles within axon
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18
Q

What is meant by threshold intensity?

A
  • Action potential can only be generated if the stimulus reaches a certain threshold intensity
  • Below this threshold, no action potential can be created
  • Once the threshold level is reached, the size of an impulse is independent of the intensity of the stimulus
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19
Q

What is the membrane potential difference at resting potential? (mV)

A

-70mV

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20
Q

What is the link between a strong stimulus and action potentials?

A

A stronger stimulus produces a greater frequency of action potentials

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21
Q

What is the refractory period?

A
  • Time delay following the passage of one action potential
  • Lasts a few milliseconds
  • Depolarisation can’t happen - Na+ channels are closed which prevents inward movement of Na+ so another impulse can’t be conducted
  • After this, repolarisation occurs - K+ channels open
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22
Q

What is the importance of the refractory period?

A

•Impulses can only flow in one direction along an axon
- so the region of axon behind the impulse can’t be depolarised
•Limits the frequency at which successive impulses can pass along an axon

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23
Q

What are nerve impulses?

A
  • Info carried in the form of electrochemical signals
  • Travel as action potentials and pass along axon in a wave of depolarisation
  • Results In changes in potential difference across the axon membrane
24
Q

What are voltage gated proteins?

A
  • Respond to changes in voltage

* Opened by depolarisation

25
Q

What is the effect of depolarisation? (Active neurone)

A
  • Na+ voltage gated proteins open
  • Na+ ions diffuse in down a concentration gradient
  • Voltage becomes +40mV
26
Q

What is the effect of repolarisation? (Active neurone)

A
  • Na+ voltage gated proteins close
  • K+ channels open
  • K+ ions flood out of axon
  • Brings it back to -70mV
27
Q

What is the effect of hyperpolarisation?

A
  • K+ channels remain open
  • Inside of axon becomes too negative (-80mV)
  • Once these channels close, resting potential can be restored
28
Q

What does the transmission speed of an impulse depend upon?

A
  • Axon diameter

* Myelin sheath

29
Q

How does an increased axon diameter increase the speed of impulse transmission?

A
  • Greater S.A. of axon membrane over which exchange of ions can occur
  • Also reduces resistance - current can glow further, increasing the length of the local circuit
30
Q

What are giant axons?

A
  • Found in a number of invertebrates
  • Thought to be involved with rapid escape responses
  • RapId transmission of impulses is needed between receptors and muscles to withdraw the animal from danger
31
Q

How does myelination increase the speed of impulse transmission?

A
  • By electrically insulating the axon
  • Impermeable to Na+ and K+ so depolarisation and action potentials can’t occur at these points
  • CAN occur at nodes of Ranvier - saltatory conduction which is faster
32
Q

What is saltatory conduction?

A

When the action potential jumps from one node to the next (in a myelinated axon)

33
Q

What are the advantages of saltatory conduction?

A
  • Increases speed of impulse transmission by up to 100 times
  • Conserves energy - Na+/K+ pump only operates at nodes so fewer ions have to be transported across membrane to restore resting potential
34
Q

How may increased temperature affect transmission speeds?

A
  • Increases rate of respiration

* Restoring resting potential requires energy from ATP - Na+/K+ pump

35
Q

Stage 1 of synaptic transmission of acetylcholine (Calcium ions)

A
  • Action potential arrives
  • Depolarisation of presynaptic membrane
  • Ca+ gated channels open
  • Ca+ ions flood into knob/bulb down a conc gradient
36
Q

Stage 2 of synaptic transmission of acetylcholine (Vesicles)

A
  • Influx of Ca+ ions causes vesicles containing acetylcholine to move towards the presynaptic membrane
  • Vesicles fuse with membrane
  • Release neurotransmitter into cleft
37
Q

Stage 3 of synaptic transmission of acetylcholine (Receptors)

A
  • Acetylcholine diffuses across cleft by exocytosis

* Binds to specific receptor proteins in postsynaptic membrane (receptors are attached to gated Na+ channels

38
Q

Stage 4 of synaptic transmission of acetylcholine (Sodium ions)

A
  • Na+ gated channels in postsynaptic membrane open up due to binding of acetylcholine cashing protein to change shape
  • Na+ flood into membrane
  • Membrane becomes depolarised which initiates an action potential
  • Impulse travels to next neurone
39
Q

Stage 5 of synaptic transmission of acetylcholine (Enzyme)

A
  • To prevent continuous production of action potentials, acetylcholinesterase (enzyme) is present in synaptic cleft
  • Enzyme hydrolyses acetylcholine into acetate and choline
  • Choline and acetate diffuse back into knob
  • Energy from ATP is used to resynthesise acetylcholine from acetic acid and choline
40
Q

Why are mitochondria needed in the presynaptic bulb/knob?

A

To produce ATP for the resynthesis of acetylcholine

41
Q

What is temporal summation? (Functions of the synapse)

A
  • Each action potential that arrives at presynaptic membrane will cause a number of vesicles to release their transmitter - accumulation of neurotransmitter
  • A number of action potentials are required before there is enough transmitter (threshold level) to initiate an action potential in the postsynaptic cell - temporal summation
42
Q

What is spatial summation? (Function of the synapse)

A
  • A number of presynaptic neurones may form synapses with one postsynaptic neurone
  • Action potentials arriving in each presynaptic neurone will release a transmitter, which builds up to threshold level and triggers a postsynaptic impulse - spatial summation
43
Q

Why can impulse only pass a synapse in one direction? (Functions of the synapse)

A

Synaptic vesicles are only present in the presynaptic knob/bulb

44
Q

What effect do organophosphates have on synaptic transmission?

A
  • Inhibit acetylcholinesterase
  • Acetylcholine is not hydrolysed and remains in cleft
  • Repeated firing of post-synaptic neurone
45
Q

What is the effect of psychoactive drugs on synaptic transmission?

A
  • Affect different neurotransmitters or their receptors - bind and block at the receptors, preventing neurotransmitters from binding
  • Affects the firing of neurones
  • This alters the brain function
46
Q

Example of phylum in which the organisms have nerve net systems

A

phylum Cnidaria

47
Q

What is a nerve net?

A
  • Simplest type of nervous system

* A diffuse network of cells that group into ganglia but do not form a brain

48
Q

What are the two types of cell in a nerve net?

A
  • Ganglion cells - provide connections in several directions
  • Sensory cells - detect stimuli
49
Q

Hydra vs Human

A 
•Nervous system type:
Hydra - nerve net
Human - CNS 
•No. of cell types in N.S.
Hydra - 2
Human - many
•Regeneration 
Hydra - rapid
Human - very slow if at all
•Myelin sheath 
Hydra - absent
Human - present 
•Conduction speed 
Hydra - slow 5ms-1
Human - fast 120ms-1
•Ability to regenerate neurones
Hydra - present 
Human - absent
50
Q

How is an action potential generated?

A

•When neurone is stimulated, voltage gated Na+ channels open
- Na+ ions flood in
•Membrane is depolarised
•Potential difference across membrane is briefly reversed, becoming positive (40mV) on the inside
•Change In polarity is known as an action potential

51
Q

What is the all or nothing law?

A

Above the threshold, the size or strength of the action potential is always the same, irrespective of the size or strength of the stimulus

52
Q

Describe the propagation of a nerve impulse

A
  • Action potential at one end opens active gated Na+ channels, causing depolarisation here
  • Depolarisation affects next part, which also depolarises and original region begins to repolarise. Na+ channels at original position are shut and inactivated
  • Repeats down the axon
  • Original region is now fully repolarised and process happens again (with a distance between the other depolarised region)
53
Q

Why do myelinated neurones use less ATP than non-myelinated neurones?

A

The sodium potassium pumps are only active at the nodes of Ranvier

54
Q

What are the two main types of neurotransmitter?

A
  • Acetylcholine

* Noradrenaline

55
Q

What are excitatory drugs?

A

•Similar shape to neurotransmitter and bring about same effect
•May inhibit enzyme that breaks down the neurotransmitter
-remains attached to postsynaptic membrane

56
Q

What are inhibitory drugs?

A
  • Bind to and block receptors on the postsynaptic membrane
  • Prevents neurotransmitters from binding
  • Can cause paralysis or death due to inability of muscles to contract

Biology🧬 (24 decks)

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